The proposed Budhi-Gandaki dam will be in one of the most seismically active areas of the world. The dam site is very close to the epicenter of very recent Gorkha earthquake measured 7.9 in Richter scale. This type of dams is highly sensitive to earthquakes. Everyone knows that the proposed Budhi-Gandaki dam is located in an area prone to big landslides, which frequently block the river resulting in impoundment of entire river flow.
By: Dr. A.B. Thapa
Implementation of big storage dam projects can provide enormously large benefits to the country. Such projects apart from generation of hydroelectric energy can provide even greater irrigation, flood control and other benefits. Unfortunately such large storage dam projects can equally be a great liability to the country if they are built and operated without following strict engineering practices to ensure complete safety.
Orville Dam disaster of the USA
Very recently the news of Orville Dam disaster had been covered by media all over the world. The Oroville Dam is an earth fill embankment dam on the Feather River in the state California of the USA. This dam is 235 meters high. It is the tallest dam in the US. The storage capacity of the reservoir is 4.4 cubic kilometers. The dam serves mainly for water supply, hydroelectricity generation and flood control. It is interesting to note that this dam has provided flood control benefit exceeding US $ 1.3 billion between the years of 1987 and 1999.
Very recently in February 2017 the main spillway was damaged after heavy rains and an anticipated failure of the dam resulted in mandatory immediate mass evacuation of people numbering about 200,000 living in the river basin downstream the dam. All those people had to flee to safety at a very short notice leaving everything behind. Evacuation order was partially lifted only after four days. People wishing to come back to their homes were at their own risk allowed to return back only after the danger of dam failure had started to recede
It is reported in media that underestimation of the maximum flood discharge and lack of proper repair and maintenance of the dam is the cause of the dam disaster.
Kulekhani Dam Safety
The Kulekhani high dam was in danger of being completely washed away just a few years after the completion of its construction. We can learn from it that even minor lapses in implementation of high dam projects could have disastrous consequences for the entire country.
Government was about to take the decision to implement the Kulekhani high dam hydropower project. It was a time when a few years earlier the world was terribly shaken by two major high dam disasters. In December 1959 the Malpasset Dam built in France had collapsed. Similarly, in 1963 in Italy the Vaiont Dam disaster was accompanied with a 200 feet high wall of water sweeping into downstream villages, wiping out everything in its path. Both disasters were consequent upon poor geology. I had published in our daily newspaper “The Rising Nepal” an article explaining that the geology of the Kulekhani area could be problematic.
Storm of Criticism
Publication of my article to my great astonishment was met by a storm of widespread criticism. Even the newspaper like “Times of India” had reported that our government establishments as well as the World Bank authorities in Washington were terribly concerned about the issue raised in my article. Government had even published a statement to repudiate my viewpoint on geology of Kulekhani. Government too had good reason to be confident about the correctness of its statement because the investigation works as well as the design of that project was done by one of the world’s leading consulting firm. It was rumored that some critics had not hesitated even to demand punitive action against the publication.
All of a sudden our country was shocked by the news that the Kulekhani high dam might be on the brink of collapse just few years after the completion of the project construction. Canadian Water Resources expert Dr. John Cooper had reported after his visit to the project site that deep cracks threatening to be extremely dangerous for the safety of the high dam have already developed over a large area just upstream dam around the intake structures. It was feared that a large mass of the right bank would slide and plunge into the reservoir triggering the giant waves overtopping the dam. It became obvious that the Kulekhani dam was almost certain to collapse if prompt action is not taken to complete the necessary engineering works in time before the onset of the coming monsoon season to prevent the dam failure. A similar type of rock sliding into the reservoir had resulted in 1963 Vaiont Dam disaster in Italy.
Implementation of extensive civil engineering works in a very short period based on the recommendation of a hastily constituted panel of top geotechnical experts from four different countries, viz the USA, Canada, Australia and Japan helped to prevent the disaster that could have resulted in many thousands of deaths apart from plunging the entire country into economic despair. How the Kulekhani dam was on the brink of collapse must serve as a lesson to our policy makers and planners.
Any one visiting the Kulekhani dam site can even now see the extensive works carried out to prevent the dam failure. The intake and its surroundings have been anchored by long cables to prevent them from sliding into the reservoir. Large areas have been cleared of loose overburdens. Special drainage tunnels have been provided to prevent the landslides.
Budhi-Gandaki High Dam Safety
Nepal is looking forward to implement in near future very ambitious 260 meters high Budhi-Gandaki double arch dam hydropower project based on design of French engineers to resolve our energy supply problem. It appears that the mammoth Budhi-Gandaki High Dam Project is proposed to be implemented turning a blind eye to irrigation and flood control benefits accruing to India despite the fact that the last BJP government of India had already constituted a high level commission under the Minister Suresh Prabhu to recommend royalty to be paid to Nepal for import of regulated water.
Budhi-Gandaki dam would be higher than the Oroville dam, which is the highest dam in the USA. Similarly, the volume of the Budhi-Gandaki storage reservoir would be exceeding the volume of the Oroville dam storage reservoir.
The proposed Budhi-Gandaki dam will be in one of the most seismically active areas of the world. The dam site is very close to the epicenter of very recent Gorkha earthquake measured 7.9 in Richter scale. This type of dams is highly sensitive to earthquakes. Everyone knows that the proposed Budhi-Gandaki dam is located in an area prone to big landslides, which frequently block the river resulting in impoundment of entire river flow. Needless to say that absolute certainty of suitability of geological condition is a prerequisite for selection of the proposed double arch dam.
The type of dam proposed for the Budhi-Gandaki project must be outright rejected if there is even a slightest possibility that the geological conditions might not be satisfactory to build this type of dam. It is obvious that due to enormity of the volume of storage reservoir the scale of the collateral damages would be too big if this dam collapsed. Lack of through geological studies had resulted in failure of double arch dam even in France itself. Similarly, the Vajon dam disaster in Italy reminds us that rigorous geological studies of reservoir area are equally important.
A Panel of Experts
The Budhi-Gandaki project, which would be impounding a vast reservoir of about five cubic kilometers, would prove to be dreadful curse to our country if the dam collapsed. Thus it is absolutely necessary that our government should constitute a panel of internationally renowned experts to review rigorously all aspects of Budhi-Gandaki project dam design to ensure that it is safe to build the proposed dam before taking final decision to implement this technically ambitious high dam project.
We should not forget the fact that even then West German Government had also constituted a panel of renowned experts under a French professor, who was chairman of the World Federation of Engineering Geology, to review the design of our Kankai high dam done under their grant assistance by very experienced German consulting firm although the height of the proposed dam was only about 80 meters.
Source : New Spotlight